Energy recovery circuit for distributed power converters in solar cells

ABSTRACT

A method of operating an inverter device configured on a back plane of a solar module, the inverter device comprising an energy recovery circuit device coupled to a rectifier circuit, the method comprising transferring a charge from a rectifier output to a storage capacitor configured in an energy recovery circuit; storing the charge at the storage capacitor for a time period associated with a reverse recovery time; and transferring the charge to an output of a DC bus structure to reduce a diode recovery loss in the rectifier circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to and is a continuation-in-partof U.S. application Ser. No. 13/660,752 filed Oct. 25, 2012. Thatapplication is herein by incorporated by reference for all purposes.

BACKGROUND OF THE DISCLOSURE

The present disclosure generally relates to integrated circuits. Moreparticularly, the present disclosure provides a method and system forinverter device including an energy recovery circuit architectureconfigured for a solar module. Merely by way of example, the inverterdevice can be coupled to a backplane of a solar module, including aplurality of solar cells. Of course, there can be other variations,modifications, and alternatives.

Since the discovery of the photoelectric effect, solar inverters havebeen designed to convert direct current (DC) electricity produced bysolar cells or panels into alternating current (AC). The circuits termedinverters originally refer to the process of constantly inverting theincoming signal from a DC source have been performing the DC to ACconversion from watts to megawatts. Since the resurgence of the PV solarpanel technologies in the early 2000's, inverters have become the pointof focus as they defined the cost, performance and reliability of solarinstallations. Clubbed with other components as part of theBalance-of-System (BOS) components the inverter plays a significant rolein defining the lifetime of the installation.

As an example, the US Department of Energy has launched the SunShot™initiative to achieve the goal of an installed cost of $1/watt (DC) forsolar systems for residential, commercial and utility-scale photovoltaic(PV) solar installations. With panel costs rapidly falling, theinverter, BOS costs and installation costs have been the focus for thePV industry. In addition the lower system efficiencies (Solar-panel togrid/end point of load), hovering around 80%, have been an area ofconcern as they contribute to significant capital expenditure and O&Mcosts. Efficient power conversion topologies that would lower the cost,improve system efficiency and performance have been sought to achievethe goal of grid parity for Leveraged cost of electricity (LCOE) for PVSolar power.

SUMMARY OF INVENTION

The present disclosure generally relates to integrated circuits. Moreparticularly, the present disclosure provides a method and system for aninverter device including an energy recovery circuit architectureconfigured for a solar module. Merely by way of example, the inverterdevice can be coupled to a backplane of a solar module, including aplurality of solar cells. Of course, there can be other variations,modifications, and alternatives.

In a specific embodiment, the present invention provides an inverterdevice configured on a back plane of a solar module. In an example, theinverter device comprises an energy recovery circuit device. The energyrecover circuit a storage device coupled to a rectifier output from arectifier circuit device. The energy recovery circuit is configured totemporarily store a reverse recovery charge and transfer the reverserecovery charge to an output of a DC bus structure to reduce a dioderecovery loss in the rectifier circuit.

In an example, the storage device comprises a capacitor configuredbetween a first terminal and a second terminal of the rectifier output.In an example, the second terminal is at a ground terminal. In anexample, the energy recovery circuit further comprises a node betweenthe capacitor and the second terminal. The node is at an output voltageof the output of the DC bus structure. In an example, the energyrecovery circuit includes a first p-n diode configured between the nodeand the second terminal. The first p-n diode is configured to maintainthe node at the output voltage. In an example, the rectifier circuitdevice comprises a full bridge diode circuit coupled with the energyrecovery circuit. In an example, the energy recovery circuit furthercomprising an inductor coupled to the first terminal. The inductor is inparallel to the storage capacitor and in series with the first p-njunction diode. In an example, the energy recovery circuit furthercomprising a second p-n junction diode provided between the first p-njunction diode and the storage capacitor. The second p-n junction diodeis coupled to an output terminal of the DC bus structure. In an example,the second p-n junction diode is configured to allow a switching currentto flow to the output terminal. In an example, the energy recoverycircuit is configured with the inverter device, which is coupled to agroup of solar cells. In an example, the group of solar cells isprovided in a solar module. In an example, the storage capacitor ismetal or ceramic filled capacitor structure having a capacitancedetermined by a frequency of switching on the rectifier circuit, thereverse recovery charge, and a voltage across the rectifier output.

In an alternative specific embodiment, the present invention provides amethod of operating an inverter device configured on a back plane of asolar module, the inverter device comprising an energy recovery circuitdevice coupled to a rectifier circuit, the method comprisingtransferring a charge from a rectifier output to a storage capacitorconfigured in an energy recovery circuit; storing the charge at thestorage capacitor for a time period associated with a reverse recoverytime; and transferring the charge to an output of a DC bus structure toreduce a diode recovery loss in the rectifier circuit. Further detailsof the present method can be found throughout the present specificationand more particularly below.

Many benefits are achieved by ways of present invention. For example,the present invention uses an integrated solar inverter device, having amaster/slave architecture, on a back plane coupled to a solar module.The present solar module is efficient and less costly than conventionalsolar modules with external inverters connected through a junction box.Additionally, the inverter device comprises a slave circuit and mastercircuit. Depending on the embodiment, one or more of the benefits can beachieved. These and other benefits will be described in more detailedthroughout the present specification and particularly below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified top view diagram of a solar module comprising aplurality of cells and associated inverters according to an embodimentof the present disclosure;

FIG. 2 is a simplified top view diagram of a module backplane coupled toa slave inverter according to an embodiment of the present disclosure;

FIG. 3 is a simplified diagram of a master chip module according to anembodiment of the present disclosure.

FIG. 4 is a simplified diagram of a slave chip module according to anembodiment of the present disclosure.

FIG. 4A is a simplified flow diagram of a master chip module and slavechip module operation according to an embodiment of the presentinvention.

FIG. 4B is a simplified flow diagram of a master chip module and slavechip module operation according to an embodiment of the presentinvention.

FIG. 5 is a more detailed of the slave circuit of FIG. 4, includingfilter, phase shifter, RERC, and boost circuit (including phase shifterand RERC) according to an embodiment of the present disclosure.

FIGS. 6, 7, and 8 are examples of inverter circuits according to anembodiment of the present disclosure.

FIG. 9 is a waveform derived from a slave circuit according to anembodiment of the present disclosure.

FIG. 10 is an overall diagram of a master circuit coupled to a pluralityof slave circuits according to an embodiment of the present disclosure.

FIG. 11 illustrates each of the voltage and current waveforms from eachof the slave circuits and an aggregation of each of the voltage andcurrent wave forms according to an embodiment of the present disclosure.

FIG. 12 illustrates solar cell elements, including a glass member, aplurality of cells, a backplane, and an inverter according to anembodiment of the present disclosure.

FIGS. 13 and 14 illustrate waveforms with switching voltages acrossrectifier bridge diodes with and without the RERC circuitry according toan embodiment of the present disclosure.

FIG. 15 illustrates a voltage/current plotted against time for thecircuitry of FIGS. 13 and 14.

FIG. 16 illustrates waveforms of a wave shaper circuit according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE DISCLOSURE

The present disclosure generally relates to integrated circuits. Moreparticularly, the present disclosure provides a method and system for aninverter device including an energy recovery circuit architectureconfigured for a solar module. Merely by way of example, the inverterdevice can be coupled to a backplane of a solar module, including aplurality of solar cells. Of course, there can be other variations,modifications, and alternatives.

As PV panel increase in rated output power, the notion of running at theMaximum Power Point (MPP) has been a preliminary requirement to maximizethe power generation. In addition “stringing” PV panels, which candiffer in their MPP points by +/−3-5% usually results in almost allpanels being run at suboptimal power points. Further the effects ofshading and soiling, which contribute to higher loss, get amplified instring topologies. As a result, central inversion and string inversiontopologies have substantially lower system efficiencies. Thesetopologies with advantages of price and reliability prove to be costlyin the long run. For most financed PV projects, the higher economic costof central inversion topologies is preferred owing to these advantagessacrificing system performance. A significant shortcoming of the centralinversion topologies is their inability to aid O&M through panel levelmonitoring and reporting. String designing, layout optimization, BOScomponent costs and EPC costs are significantly higher for centralinversion topologies which are usually ignored while calculating theutility of such topologies.

Distributed converters or micro-inverters on the other hand perform thetask of inversion at the panel-level enabling the system to deliver theoptimal efficiency in all weather conditions. Since the output of eachmicro-inverter is a grid synced AC power at the desired voltage,micro-inverters are usually daisy chained to aggregate the AC currentfrom each panel. Micro-inverters eliminate mis-match losses, suboptimalpower point losses and significantly lower the effect of shading andsoiling losses. In addition they bring the benefits of panel monitoringand reporting to aid O&M. Micro-inverter performance against othertopologies is as shown below.

In an example, certain challenges face distributed power converters.Micro-inverter solutions have been challenged on the aspects of cost andreliability. Several first generation micro-inverter solutions have beenperceived as significantly costly and unreliable. Reliability concernsseverely hinder the adoption of micro-inverters in commercial andutility-scale segments where field failures would result in significantcosts to repair and replace. Most micro-inverter companies however havebeen producing HALT/ALT and field trial data to prove their reliability.Concerns of adopting a “new technology” with significant cost impact isexpected to abide within the next couple of years as more fieldperformance data becomes available. Micro-inverters, while costeffective at the system-level, are often termed the higher costalternative when inverter-to-inverter prices are compared.

As micro-inverters gained prominence in the PV solar market initially inthe residential and small commercial (<15 KW) PV installations, thenotion of developing an integrated AC panel that significantly reducesthe cost while significantly lowering installation costs and remainingBOM costs is being pursued jointly by major panel manufacturers andmicro-inverter companies. This approach still allows for cleardistinction of liability between the panel and the micro-inverter incase of a failure. The notion of an integrated solution however suffersfrom major disadvantages as there are no significant cost, performanceand reliability benefits. There has been a significant discussion in theindustry as to what exactly constitutes an “AC Panel” and how it canachieve the $1/watt cost to normalize PV solar LCOE by the end of thedecade. In addition these approaches keep the solution at the systemlevel, slightly out of the reach of custom ASICs that can lower the costsignificantly while improving reliability.

In an example, the AC panel desirably focuses on the core issues of costand reliability while striving to improve the performance of the “ACPanel”. In addition the fundamental power conversion architecture needsto provide for custom ASICs with lagging processes to significantlylower cost and much higher reliability. The Eagle-Black plane integratedinverter AC panel described in the next chapter is the next generationAC panel technology that would significantly alter the solutionlandscape for PV Solar installations.

In an example, the present inverter device can be integrated into theback plane of a solar panel to overcome the challenges facing the ACpanel technology. The present panel is defined by a holistic approach tothe AC panel solution with cost, reliability and performance beingtackled simultaneously in the product design. As observed earlier costreduction of inversion technology is only possible through custom ASICwhich are generally difficult for power electronic circuits. Multi-chipmodules with expensive packaging technologies are usually the chosenavenue to develop custom power circuits at lower cost. The present paneltechnology however relies on an innovative Master/Slave architecture toimplement “nano” inversion on the DC power generated by a group of cellsin the PV panels. Since the power handled by the cells is lower thepresent AC panel, comprises of breakthrough DC-DC boost circuit thatachieves over 20×-40× voltage boosting at higher than 98% efficiency. Inaddition the circuit uses innovative “energy recovery circuits” toeliminate the use of expensive SiC diodes in the output bridges andreplace them with inexpensive Schottky diodes. This innovative circuitalso enables the entire solution to be packaged in an ASIC with laggingedge IC fabrication processes delivering superior performance at afraction of the cost.

The present panel technology solution has a “Master” control andcommunication ASIC that works in tandem with up to 24 “Slave” inverterASICs. The master/slave AC panel topology is a highly scalable solutionthat can be implemented in PV panels of 60 cells, 72 cells or 90 cellsto deliver 120V/240V/277V AC panels. These AC panels would beindependently grid-tied to enable installation all the way from a 300W-1 MW. As each AC panel comes completely integrated with a grounded ACoutput, the system assembly and installation process becomes completelysimple and extremely safe.

The Master/Slave topology consists of one single Master ASIC controllingthe Slave ASICs, which are connected to a group of cells in the ACpanel. This is achieved through the “Back Plane” which is essentially agrid array of cell connections that optimizes their placement to groupthe cells. Each cell group is expected to deliver at least 4-7V DC atthe input of the Slave ASIC. The details of the “Back Plane” areexplained in the following section.

The AC panel master/slave topology reduces the need for expensivemagnetic components as well as energy storing capacitors. The MasterASIC of the AC panel to monitor the grid for the requisite voltage andfrequency parameters and enables and disables the slave invertersaccordingly. Cells in the panel can be separated into arrays of 10 or 12(depending on Poly silicon/Mono crystalline/Thin film cells) into acustom designed “Back Plane” that optimizes the routing length from eachgroup of cells to the input of their corresponding Slave inverter. Asthe number of cells in a group is determined by the requisite voltageinput to the Slave inverter, AC panels of various output power arepossible. As each Master ASIC can control up to 12 Slave inverters, ACpanels ranging from 240 W-1.4KW can be designed. The limitation on panelsize would then be determined by the mechanical constraints thanelectrical constraints. In addition, optimal cost savings could beachieved around the 640 W systems with 277V outputs, which would enable480V 3-phase systems.

FIG. 1 is a simplified top view diagram of a solar module comprising aplurality of cells and associated inverters according to an embodimentof the present disclosure. As shown in the Figure above, the presentplane inverter architecture breaks the inversion process into DC boostwith MPPT and generation of a 120V/240V/277V rectified DC waveform fromeach group of cells in the panel and aggregating their currents in theAC un-folder circuit controlled by the Master ASIC. The optimization ofthe cell placement is achieved by the custom designed “Back Plane”enables the Slave inverter to have a extremely low profile planar DCboost transformer integrated along with the ARC filter inductor. The DCboost circuit described in the following sections, achieves 20×-40×boost using a proprietary switching technique that achieves “zerovoltage” switching at >200 Khz switching frequencies. The Slave inverteralso senses the voltage and current of the panel group to run acell-group level MPPT optimizing the power from each cell group. Thisenables the inverter powered AC panel to deliver significantly higherperformance than AC panels integrated with micro-inverters. Theencapsulation of all desirable circuits into custom ASIC significantlyimproves the reliability of the AC panel, well beyond the customary 25years. This higher reliability also comes with increased performance andsubstantially lower cost.

FIG. 2 is a simplified top view diagram of a module backplane coupled toa slave inverter according to an embodiment of the present disclosure.The “Back Plane” of the AC panel is custom designed grid arrangementthat groups the cells on the panel into groups driving the power circuitof a Slave inverter. The “Back Plane” (BP) in an integrated part of theelectrical circuit as it plays a significant role in optimizing the celllayout.

The BP allows for minor improvements in the integration of theMaster/Slave inverters by choosing the cell groups for each Slaveinverter. The physical proximity of each cell group to the Slaveinverter enables lower cost of tab wires while providing for “nodes” onto which the cells can be directly placed during panel assembly. The BPcircuit is an addition plane layer hooked to the main inverter PCB whichholds the Master/Slave ASICs. The BP shape and layout are determined bythe characteristics of the cells being used for the AC panel. The numberof nodes could be much smaller for a “Thin film” panel as most of theindividual cells are combined in parallel, than that of a “Poly-siliconpanel” where in most of the individual cells are connected in series. Asa result the nodes on each individual cell branch are defined by thecell material and needs to be optimized based the desired cell outputpower and voltage. The aim of the BP is to ensure optimal cell groupingso that the input DC voltage from them is at least 4V. The BP also needsto ensure minimal losses on the tab wires by minimizing their lengthsbefore reaching the input of the Slave inverters.

In a specific embodiment, the present invention provides a solar moduledevice with a back plane integrated inverter device. The device includesa substrate member comprising a front side and a back-side. The devicehas a plurality of solar cells, which comprising a first group of solarcells connected in a first serial configuration and a second group ofsolar cells connected in a second serial configuration. The device has atab wire configuration formed overlying the front side of the substratemember. The tab wire comprises a first interconnect coupled to the firstset of solar cells in the first serial configuration and a secondinterconnection coupled to the second set of solar cells in the secondserial configuration. The device has an inverter device coupled to aback side of the substrate member. The inverter device comprises a firstset of connections coupled to the first interconnection and a second setof connections coupled to the second set of connections.

FIG. 3 is a simplified diagram of a master chip module according to anembodiment of the present disclosure. As shown, the master chip moduleis a master ASIC. The Master ASIC hosts the central control part of theAC Panel. The Master ASIC has the following features.

1. Controls up to 24 Slave inverters and the integrated AC un-folder.

2. Control algorithms for both Grid-Tie and Off-grid Applications withinternal sync.

3. Check for IEEE 1547/UL1741 Grid Conditions and enable/disable thepower production of the Panel on an abnormal grid/load or low powercondition.

4. Control the current output of each of the Inverter and enable/disablethe Slave inverters in event of an abnormal grid/load condition.

5. Absolute and pre-emptive control on what is put out on the gridside/load side of the inverter.

6. Monitor the individual Inverter power production as well ascumulative power production of AC panel at the output.

7. Produce Proportional reference rectified grid Voltage for the SlaveControl ASIC to produce 120/240/277V RMS Rectified Grid Waveform.

8. Synchronize the output un-folder to the incoming grid voltage or loadside commutation to produce a clean sinusoidal AC waveform with minimalTHD.

9. Communications on Wired/Wireless physical layers to any central datacollection system.

In an example, the Master ASIC measures the Voltage and Current signalsoutput from each of the Slave inverters and produces a proportional MPPTset point for each of them. An architectural block diagram of the MasterASIC is as shown.

The Slave ASIC is the Power Production Control ASIC of the Inverter fora given group of cells on the panel. It is receives its DC input from aserial or parallel group of cells. The Features of the Slave inverterASIC are as follows.

1. Monitor the cell group Voltage and Current.

2. MPPT Control the cell group Current/Voltage to ensure that theyoperate at the MPP point.

3. Collate the Current/Voltage/Temperature Data for monitoring &reporting through the Master ASIC.

4. Produce a Rectified Sine Waveform for the output un-folder bridge at120V/240V/277V as desired by the AC panel configuration.

5. Maintain a high quality, low harmonic distortion (THD) outputrectified Sine Waveform for grid interconnection or load sidecommutation by the master ASIC.

6. High speed precision Mixed Signal Control loop to track the incomingreference signal from the master ASIC.

7. Work in the Average Current mode controller for Grid Tied Operationand Voltage Mode Peak Current Mode Control for Off Grid Applications.

8. A RISC Processor to have precision control state machines and datacollation engines.

FIG. 4 is a simplified diagram of a slave chip module according to anembodiment of the present disclosure. As shown, the Block Diagram of thecontrol ASIC is shown.

In a specific embodiment, the present invention provides a distributedpower converter for a solar module. The system has a plurality of slavecircuits, each if which is coupled to a solar cell group. Each of theslave circuits has an input comprising a DC input from a solar cellgroup. The slave circuit has a preliminary boost circuit coupled to theinput. The preliminary boost circuit is configured to boost an inputvoltage from the input from the solar cell group to an intermediaryvoltage. The slave circuit has a DC boost circuit coupled to thepreliminary boost circuit and is configured to boost the intermediaryvoltage to an AC RMS peak voltage. The slave circuit has a rectifiercircuit coupled to the DC boost circuit and configured to wave shape theDC output to a half wave rectified DC waveform and is preferablyconfigured to reduce a diode recovery loss in the rectifier circuit.

In an example, the system has an output coupled to a DC bus structureand a master circuit. The master circuit is coupled to each of the slavecircuits via the DC bus structure. The master circuit is configured togenerate a timing signal to synchronize each of the slave circuits,which generate a synchronized half wave rectified DC waveform. Theplurality of slave circuits output a resulting half wave rectified DCwaveform having an amplitude characterized by a combination of each ofthe amplitudes from each of the slave circuits.

In an example, each input comprises a first terminal and a secondterminal. Each of the preliminary boost circuits comprises an inductivestorage coupled to a capacitive storage coupled within a boost circuit.Each of the DC boost circuit comprises a phase shift full bridge boostcircuit or an advanced boost circuit achieving Zero-Voltage-Switching(ZVS) or Zero-Current-Switching (ZCS) or both ZVS and ZCS. Each of therectifier circuits comprises a four-diode bridge circuit coupled with anenergy recovery circuit. Each of the outputs comprises a pair ofterminals coupled to the DC bus structure.

In an example, the system has various voltages. As an example, the inputcomprises a voltage of at last four (4) volts. In an example, theintermediary voltage ranges from about 15 volts to 20 volts. In anexample, the half wave rectified DC waveform has a voltage ranging fromabout 160 volts to 350 volts. In an example, each of the half waverectified DC waveforms is characterized by a substantially similarvoltage to result in aggregated current waveform, which is substantiallyequal to a number of currents resulting from each of the half waverectified DC waveforms. The number is equal to a number of slavecircuits in the plurality of slave circuits.

In an example, each group of solar cells comprises a slave invertercircuit such that output power is optimized from the group of the solarcells configured in a serial manner and directly coupled to the slavecircuit. In an example, each of the slave circuits provides a galvanicisolation between a DC source derived from each group of the solar cellsand a combined AC supply, which is either from a grid source or areference AC signal generated by another device. In an example each ofslave inverter circuits is suspended with a common signal and preventedfrom performing an DC to AC inversion to enhance safety when connectedto the grid source (Anti-islanding). In an example, the distributedpower converter is provided a backside of a substrate of one of thesolar modules and is substantially free from a junction box or poweraggregator. In an example, the master circuit is configured to unfold avoltage and a current waveform on the DC bus structure.

In an alternative embodiment, a solar module device with the mastercircuit generates the timing signal to synchronize each of thesynchronized half wave rectified DC waveform generated by each of theslave circuits to a grid AC signal or a reference AC signal to allow theDC-AC power conversion of a plurality of solar cell groups provided in amodule in an on-grid application and an off-grid application.

In an example, the master circuit is configured for at least onehouse-keeping operation to regulate a performance of each of the slavecircuits in response to a changes in an external condition on the gridAC signal when configured in the on-grid mode. In an example, the mastercircuit is configured for at least one house-keeping operation toregulate a performance of each of the slave circuits in response to achange in an external conditions on the reference AC signal whenconfigured in the off-grid mode. In an example, the synchronizedhalf-wave rectified DC waveform is converted into a AC voltage and acurrent waveform to feed power into a utility grid for an on-gridoperation or a micro-grid for an off-grid application through aselection of an AC un-folding circuit provided per a feature of aconfigured application. In an example, the master circuit and theun-folding circuit uses a combination of a sense circuit to monitor thegrid AC signal or reference AC signal to generate a reference signal ofthe slave circuit to generate the synchronized half-wave rectified DCwaveform to add up a power output from each cell group.

In an example, the present invention provides a method of using adistributed power converter for a solar module. The method includesgenerating a DC output from a solar cell group from a plurality of solarcell groups provided in a module and receiving the DC output at an inputof a preliminary boost circuit coupled to the input. The method includesboosting, using the preliminary boost circuit, an input voltage from theinput from the solar cell group to an intermediary voltage. The methodincludes boosting, using the DC boost circuit, the intermediary voltageto an AC RMS peak voltage. The method includes wave-shaping the DCoutput to a half wave rectified DC waveform while reducing a dioderecovery loss in the rectifier circuit and generate a timing signal froma master circuit to synchronize the half wave rectified DC waveform togenerate a synchronized half wave rectified DC waveform. The methodincludes combining the synchronized half wave rectified DC waveform witha plurality of other synchronized half wave rectified DC waveforms tooutput a resulting half wave rectified DC waveform having an amplitudecharacterized by a combination of each amplitude from each ofsynchronized half wave rectified DC waveforms. Further details of thepresent method can be found throughout the present specification andmore particularly below.

FIG. 4A is a simplified flow diagram of a master chip module and slavechip module operation according to an embodiment of the presentinvention.

FIG. 4B is a simplified flow diagram of a master chip module and slavechip module operation according to an embodiment of the presentinvention.

FIG. 5 is a more detailed of the slave circuit of FIG. 4, includingfilter, phase shifter, RERC, and boost circuit (including phase shifterand RERC) according to an embodiment of the present disclosure. Asshown, the Booster Stage is the key part of the Slave inverter ASIC thatenables 20×-40× voltage boost at high efficiency. In addition this Boostconverter circuit is designed to use low voltage MOSFETs, which enablethe encapsulation of the power circuit in a lagging edge processtechnology. The cost reduction is further achieved through the use ofinexpensive Ultrafast Silicon PN Junction diodes in place of SiC diodesand an innovative “Rectifier Energy Recovery Circuit” minimizes thelosses delivering greater than 98% efficiency. The Boost circuitconsists of the 3 stages show, above which are described in detailbelow.

Phase Shift Full Bridge Converter

The PSFB (Phase Shift Full Bridge) Converter works with a constant deadtime lagging phase leg average current mode control system. The PSFB andthe RERC together use the Magnetizing inductance of the transformeralong with the Primary and Secondary parasitics of the transformer tosoft switch the primary side switching components (M3, M4, M5, M6) in afashion that the ZVS operation is valid for any duty cycle. Regulardesigns involving the PSFB use the leakage inductance of the transformeror an additional inductor in the primary path to achieve ZVS on theprimary side switching components. The main advantage of this circuit isthat the Diodes D1 thru D4, which rectify the output of the transformerdoes not freewheel with the Inductor. Hence full DiscontinuousConduction Mode (DCM) is achieved on the rectifier Diodes.

The DCM mode of operation is crucial for the transformer to cut off at apredefined interval exposing the magnetizing inductance to the primaryside components for a Zero Voltage Switching during dead times betweenM3, M4 and M5, M6. Zero Voltage Switching of primary side components ishighly desirable as these components can be switched at a much highfrequency thereby reducing the size of the transformer, inductor andcapacitors needed in the circuit. The Slave inverter can effectively bebuilt with integrated magnetic switching at >250 Khz to about 2 MHzlimited with the availability of Ferrite Materials.

The unique feature of the circuit is to use the primary magnetizinginductance which is lossless to actually freewheel the primary part ofthe circuit to reduce the switching losses of the Converter considerablyto an insignificant level and reduce the common mode conduction loss ofthe primary side switching components and use minimum parasitics on theswitches to achieve ZVS Commutation. The energy storage in thetransformer becomes very less owing to a higher inductance value usedfor ZVS commutation and nullifies the need for a leakage inductancethereby tightly coupling the Primary and Secondary windings of thetransformer with a high coefficient of coupling. The Primary SideSwitching circuit operates satisfactorily in ZVS mode for a PrimaryLeakage Inductance in the range of 0-10% of the Primary Magnetizinginductance of the transformer indicating that the leakage inductance hasinsignificant role in the commutation of the ZVS transition of thePrimary Side Switching Components.

Rectifier Energy Recovery Circuit

The Rectifier Energy Recovery Circuit (RERC) is a crucial part of thePSFB Circuit to operate in the ZVS region. The RERC removes reverserecovery charge if any on the rectifier diodes (D1 thru D4) thusenabling the use of regular inexpensive Silicon PN Junction diodesagainst expensive high voltage SiC Schottky Diodes.

The RERC recovers the junction energy of diodes D1 thru D6 in to thecapacitor C1 and then transfers the energy to the output thus making thediodes D1 thru D4 behave like a majority carrier device as a Schottkydiode.

The RERC also free wheels the inductor making D1 thru D4 always stay inDCM irrespective of the output Power Level. Making Diodes D1 thru D4 tostay in DCM is crucial for the Converter as this nullifies the switchinglosses to an insignificant value and hence the Converter can be operatedat a significantly higher frequency reducing the Inductive andCapacitive components in the circuit thereby reducing the form factorand size of the circuit considerably.

ARC Filter Stage

The Active Ripple Cancellation (ARC) Filter cancels the DC CurrentRipple found on the input Solar Panel Voltage. M1 and M2 switchesoperate on a principle of a bidirectional DC-DC Converter. The ARCFilter Charges Capacitor C2 to a stipulated voltage during lowconduction states of the PSFB and will discharge the capacitor duringhigh conduction states of the PSFB Converter.

The ARC filter operates the switches in a fully Zero Voltage SwitchedOperation using a Constant Dead-time Average Current Mode Control. TheARC Filter intends to replace Aluminum Electrolytic Capacitors with ahigh reliability Metal Film or Ceramic Capacitor of a lower capacitanceValue.

The Capacitor C2 is fully utilized on the Voltage Scale between Vin andVmax Rating of the Capacitor. The ARC Filter filters out the 120 Hz/100Hz Line frequency ripple introduced by the PSFB minimizing the currentripple seen by the Solar Panel.

AC Un-Folder Circuit

The AC Un-Folder Circuit is desirable for this implementation. TheAggregated power of each of the Nano Inverter Boost Circuit is availableon the AC un-folder Input V+/V−. Since the output of the boost circuitis a rectified sine wave, the Un-folder circuit converts the incomingrectified sine wave to line frequency AC sine wave. In principle, theun-folder circuit has to prevent any rectified sine waveform from theline to enter into the Boost Circuit Output when the boost circuit isnot producing any power. Though the un-folder circuit is hard switched,the switching losses are negligible due to the low switching frequency,which is usually the line frequency (50/60 Hz).

In the following sections, various schemes of implementing the ACUn-folder are specified, which are also referred to in FIGS. 6, 7, and8.

MOSFET Un-Folder

In this Scheme, the Mosfets M1, M2, M3, M4 form the unfoldingcommutation circuit. When the voltage between Line and Neutral ispositive, M1, M3, M5 are on and when the Line and Neutral is negative,M2, M4, M5 are on. The Line Filter comprising of L1, C1, C2, C3 filterout the switching transient effects from the Unfolding Circuit. Diode D1forms a Reverse Blocking Diode, which does not allow the body dioderectification to enter into the boost circuit output when the system isnot producing any power. To reduce the losses of the Diode D1, Switch M5is used, switch M5 is on when there is power production from the system.This Un-Folding Scheme allows for a low conduction loss implementationin voltages up to 250V Rms. The Un-Folder Dead time of thisimplementation can be less than a 200 ns making the Un-Folder output avery clean Sine wave of less than 2% THD. Since the output switches canbe controlled, the system can be shut off at any point on the linecycle.

IGBT Un-Folder

In this scheme, the IGBT's Q1, Q2, Q3, Q4 form the unfolding commutationcircuit. When the voltage between, Line and Neutral is positive, Q1, Q3,Q5 are on and when the Line and Neutral is negative, Q2, Q4, Q5 are on.The Line Filter comprising of L2, C4, C5, C6 filter out the switchingtransient effects from the Unfolding Circuit. Diode D1 forms a ReverseBlocking Diode, which does not allow the body diode rectification toenter into the boost circuit output when the system is not producing anypower. To reduce the losses of the Diode D1, switch Q5 is used, switchQ5 is on when there is power production from the system. This Un-FoldingScheme allows for a low conduction loss implementation in voltagesbetween 400V up to 600V Rms. The Un-Folder Dead time of thisimplementation can be less than a 500 ns making the Un-Folder output avery clean Sine wave of less than 3% THD. The system will be rugged asthe devices Q1, Q2, Q3, Q4, will have a short circuit rating for aperiod of 10 us. Since the output switches can be controlled, the systemcan be shut off at any point on the line cycle.

SCR Un-Folder

In this Scheme, the SCR's T1, T2, T3, T4 form the unfolding commutationcircuit. When the voltage between, the Line and Neutral is positive, T1,T3 are on. When the Line and Neutral is negative, T2, T45 are on. TheLine Filter comprising of L3, C7, C8, C9 filter out the switchingtransient effects from the unfolding circuit. Since SCR's areunidirectional conduction devices, the system does not require ablocking diode. This un-folding Scheme allows for a low conduction lossimplementation in voltages between 100V up to 600V Rms. The un-folderdead time of this implementation can be less than a 100 us making itoutput a Sine wave of slightly less than 5% THD. The system will berugged as the devices T1, T2, T3, and T4 will have a short circuitrating for a period of 10 us. Since the output switches can becontrolled on and not off, the system can be shutoff only at the zerocross of the line cycle.

The key feature of the AC Panel remains the integration of the powergenerated from each of the Slave inverters by the Master. Theintegration and control aspect of the AC panel remains desirable aspower aggregation at small currents is quite difficult. The Master/Slavearchitecture of the AC panel has 2 architectural features in place toenable power aggregation with simple control algorithms.

1. Reference synced rectified DC output waveform at uniform voltage fromSlave inverters

2. Synced current wave form matching the reference signal generated byMaster from the Slaves

For instance to generate a 120V AC at the output of the AC un-folder theMaster would set the rectified DC voltages of the Slave inverters at169V RMS.

FIG. 9 is a waveform derived from a slave circuit according to anembodiment of the present disclosure. The output voltage waveform fromeach of the Slave inverters for a 120V AC output is as shown.

FIG. 10 is an overall diagram of a master circuit coupled to a pluralityof slave circuits according to an embodiment of the present disclosure.In addition to the voltage set point, the reference sync signal, whichwould be a low voltage stepped down grid voltage of 2.5V p-p forgrid-tied application and master generated 2.5Vp-p rectified sine wavefor off-grid application, ensures an identical voltage waveform fromeach of the Slave inverters. The Slave inverters further generate amatching current waveform depending on the current set point provided bythe Master corresponding to their MPP points. These reference pointsalso help the Master enable/disable the Slave inverter in less 10 us, tocomply with the anti-islanding requirements for various safetystandards. In conjunction with the reference signal, voltage set pointand current point a fool-proof shutoff can be implemented in the Slaveinverters with relatively simple control loops. At the same time, thesteady state run time performance is made flawless with these referencesignals from the Master, making a the control loops for the Slaveabsolutely rudimentary. It is important to note that the MPP points foreach of the Slave inverters is determined by the Master which has muchhigher compute power than the AMS controllers in the Slaves. The Mastersamples the current and voltage values from each of the Slave devices atthe beginning of each AC cycle to determine their corresponding setpoints. The following figure shows the circuit of the interconnection ofthe Slave inverter outputs aggregated to feed the AC un-folder (MOSFETun-folder shown here). The parallel interconnection is possible due tothe identical waveforms generated from each of the Slaves. The currentwaveform generated from each of the Slaves is also a rectified sinewave, synced up to the reference signal provided by the master. Theaggregation of the current waveforms at various amplitude levels doesnot have any bearing on the output THD, as they are phase aligned andfrequency correlated. The input of the AC un-folder with an activeMOSFET circuit ensures that the aggregated rectified DC current andvoltage waveforms are filtered to ensure a smooth sine wave. The ACun-folder circuit can thus be a simple commutation circuit that convertsthe rectified DC voltage and current waveforms into the desired ACwaveform at requisite line frequency. The output line filters aredesigned to provide 120V/240V/277V single-phase or 240V split phase ACoutputs directly from the panel. This simplifies the output AC cabledesign, which can be any regular grounded AC connector with 15 A currentrating. The following figure illustrates the independent currentwave-forms from the Slave inverters plotted against the referencevoltage waveform. The last waveform in the figure shows the aggregatedAC panel voltage and current waveform.

FIG. 11 illustrates each of the voltage and current waveforms from eachof the slave circuits and an aggregation of each of the voltage andcurrent wave forms according to an embodiment of the present disclosure.Note: Legend: ‘A’ waveform is the grid Voltage. ‘B’ waveform is the 100×Current Waveform.

FIG. 12 illustrates an AC module or panel, including glass/frame, solarcells, backplane, and inverter according to an embodiment of the presentinvention. As shown, the AC panel overcomes challenges limiting the widespread adoption of AC panels in solar PV installations. In each of thethree significant aspects—cost, reliability and performance, the ACpanel solution fares far better than current solutions. Elimination ofjunction box diodes saves 2-3% of power loss straightaway in thisexample. Each cell group performing at MPPT significantly lowers soilinglosses making the solar panel can work even on partially shadedconditions providing a higher MPP performance over a regularmicro-inverter/central inverter under the same conditions. Optimizationor improvement of cell group performance improves the overall MPPperformance by 5-10% in an example. Slave inverters deliver greater than98% efficiency with PSFB and RERC circuits. Overall efficiency higherthan 97% from the panel delivering AC in this example.

ZVS switching delivers high efficiency even for 240V/277V systems withabout 40× boosting in an example. Overall system performance surpassesthe combination of DC Optimizer with Central inverter or regularmicro-inverter by about 5-10% depending on conditions. Overall SystemEfficiency in commercial scale can be improved from 91-93% to about96%(Limited by AC Cable Design) under field Conditions. In an example,elimination of cable costs lowers AC panel cost by about 20% in anexample. Elimination of enclosure for the inverter eliminates 5% of thecost in an example. Elimination of junction box in the panel saves about$15. Elimination of DC cable connectors saves about $7 in an example.Elimination of assembly costs related to Panel and micro-inverter in anexample. Combination of back panel and integrated Inverter PCB savespanel costs in an example. Encapsulation of the power circuit in acustom ASIC cuts the cost of power circuit by 60% of its discretesolution in an example. Encapsulation of the control and communicationASIC lowers the cost of the Master controller to about 50% of thecurrent discrete solution in an example. Inverter based Master/Slavearchitecture lowers the cost of magnetic by 50% in an example. Inverterbased Master/Slave architecture replaces Metal Film Storage of Linefrequency Power with highly inert Ceramic Capacitor lowering the cost by80% in an example. The solution nears a $0.12/watt DC installed forInverter and BOS in an example. Elimination of the DC Ground removes theneed for DC GFDI which lowers the BOS Cost by 5% in an example.

In an example, opto-isolators and discrete gate drive circuits areeliminated improving MTBF. Integrated planar magnetic components improvethe Mean Time Between Failure (MTBF), field repeatability and simplifiedproduction process. Encapsulation of power circuit on Slave ASICimproves reliability. Encapsulation of control and sense circuits inslave ASIC eliminates discrete components prone to degradation.Elimination of high capacity metal film capacitor with automotive gradeceramic capacitors improve the reliability and power density of theproduct by a major margin.

In an example, the present invention provides a method of assembling asolar module device with a back plane integrated inverter device. Themethod comprises providing a substrate member comprising a front sideand a back side. The substrate member has a tab wire configuration(e.g., aluminum, copper material) thereon. The method includes couplinga plurality of solar cells, the plurality of solar cells comprising afirst group of solar cells connected in a first serial configuration anda second group of solar cells connected in a second serial configurationsuch that the tab wire configuration is formed overlying the front sideof the substrate member. The tab wire comprises a first interconnectcoupled to the first set of solar cells in the first serialconfiguration and a second interconnection coupled to the second set ofsolar cells in the second serial configuration. The method includescoupling an inverter device to a back side of the substrate member. Theinverter device comprises a first set of connections coupled to thefirst interconnection and a second set of connections coupled to thesecond set of connections. The first group of solar cells comprises afirst DC slave circuit and the second group of solar cells comprising asecond DC slave circuit. In an example, the solar module comprises asandwiched structure including backplane, solar cells, tab wire, andintegrated inverter in a single assembly. The substrate is made ofglass, epoxy resin, or other electrically insulating material in anexample.

Referring now to FIGS. 13, 14, and 15, as shown are waveforms from afull-bridge rectifier circuit at the secondary of the transformer thatconverts 1666 digital sine wave samples into absolute (only positivepulses) pulses. As a result the diodes switch 1666 time during each sinewave cycle. Part of the energy transferred across the transformer by thePSFB is lost every time a diode in the rectifier bridge switches. Thecommon diode power loss is due to the reverse recovery charge present onthe diode at the time of switching. The reverse recovery energy loss(FIG. 15) is given by Vm*Irrm*trr/2. Refer to the image for the actualloss. As the switching times are high this loss is pretty significant.The Rectifier Energy Recovery Circuit, actually adds additional passiveelements to snub these losses. An additional capacitor C3 in the snubbercircuit is charged during the reverse recovery period and recycled intothe output during the time the diode actually conducts. Over a period of1666 switching cycles 3-4% of power loss could be saved through the RERCcircuit. Waveforms with the switching voltages across the rectifierbridge diodes with and without the RERC circuitry are provided by FIGS.13 and 14)

Referring to FIG. 16, the present wave shaper circuit includes a phaseshift full bridge circuit consisting of 4 power MOSFETs coupled to atransformer. The MOSFETS are switched alternatively (upper leg on, lowerleg off and vice versa) and the waveforms of the individual legs arephase shifted. The relative phase shift in turning on/off the MOSFETSgenerates a digital sine wave at the input of the transformer. A seriesof such digital sine wave generates a half-wave voltage waveform of 120Hz/100 Hz (for 60 Hz/50 Hz line frequency) across the inductor at theoutput of the secondary side of the transformer. The current waveformacross the output is also a half wave rectified sine wave ofcorresponding amplitude. For a 60 Hz line frequency about 1666 samplesof digital sine wave (waveform 5) generate 2 of the half-wave rectifiedsine waves. Phase shifting the switching of the MOSFETs in thefull-bridge legs with varying phase results in the Zero VoltageSwitching lowering the conduction losses. At the same PSFB operating inZVS mode also allows higher frequency switching thereby reducing theswitching losses.

In an example, the present invention provides an inverter device. Thedevice includes a slave inverter circuit configured to generate arectified DC waveform and an active ripple cancellation boost circuitcoupled to the slave inverter circuit and being configured coupled to aDC source from a plurality of solar cells and configured to filter an ACcurrent ripple back to the DC source and boost the DC voltage to anintermediary 12-15 voltage range. The device also has a wave shapercircuit coupled to the slave inverter circuit and comprising a phaseshift zero voltage switching full bridge circuit and a rectifier energyrecovery circuit. The phase shift zero voltage switching full bridgecircuit is configured to shape the DC source to a half wave rectified120V to 240V waveform. The rectifier energy recovery circuit isconfigured to recovery energy during a switching operation to causeformation of the waveform. The device also includes an analog mixedsignal or digital controller module configured to generate a PWMwaveform and synchronize the rectified waveform to a grid voltage andconfigured to manage a plurality of sense circuits coupled to aplurality of solar cells to record a cell group voltage and cell groupcurrent.

In a specific embodiment, the inverter device has variations. Theinverter device further comprising a master control module configured toa plurality of analog mixed signal or digital controller modules. Themaster control module is configured to generate a reference signal foreach of the analog mixed signal control modules and turn off/on therectified waveform from each of the inverter devices to a power-linegrid. The master controller module comprising a detector device coupledto the power-line grid to measure a grid voltage and a grid frequency atany given time. The master control module is configured to turn on/offeach of the inverter devices using information from the grid voltageand/or the grid frequency. The master controller module is configured ona solar module by attachment to a backplane of the solar module. Thebackplane being is substantially free from a junction box or poweraggregator. The inverter device further comprises a plurality of solarcell groups, each of the solar cell groups having a DC input to the DCslave circuit. The master controller is configured to control aun-folder circuit, which comprise an H-bridge circuit with one of anSCR, MOSFET, or an IGBT circuit. The un-folder circuit is controlledwith a closed loop control algorithm for delivery of power to apower-line grid by aggregating a plurality of current waveformsgenerated by a plurality of slave inverter circuits.

In an alternative example, the master controller and the analog mixedsignal or digital controllers are configured to communicate to exchangea plurality of reference signals and at least one voltage/current levelfrom of each of the solar cell groups. The master controller generates areference voltage waveform proportional to a power line grid voltagewithin a determined desired limit at the power line grid frequency. Themaster controller generates an instant shutoff signal which whenreceived by the analog mixed signal or digital controller power down aplurality of switching circuits of the slave inverter circuit within 500milliseconds of an initiation of the generation of the instant shutoffsignal. The master controller generates an additional sine-wavemodulated onto an output voltage waveform to distort a power-line gridvoltage waveform which in a presence of a power line grid is free fromany alteration of the power line grid voltage waveform or the additionalsine wave modulated onto the output voltage waveform distorts the outputvoltage waveform in absence of the power line grid to initiate the shutoff of the slave inverter circuit.

In an example, the slave inverter circuit controlled by an analog mixedsignal or digital controller continuously monitors a power output from acell group coupled to the slave inverter circuit to maximize the poweroutput by varying a power level and tracking a maximum power point(MPPT) of the cell group. The slave inverter circuit controlled by ananalog mixed signal or digital controller maximizes the power output toa varying power level caused by a change in irradiation provided on thecell group. The slave inverter circuit controller by an analog mixedsignal or digital controller comprises phase lock loop (PLL) circuit tosynchronize a reference voltage sampled by a master circuit to shape anoutput current and a voltage waveform. The slave circuit comprises apower loss reduction circuit configured to reduce an energy loss in adiode bridge generating the half-wave rectified waveform, the energyloss circuit being provided by a CMOS circuit or SiC circuit.

In an example, the back plane comprises a plurality of DC inputs fromthe solar cell groups fed into a printed circuit board of the back planeat a plurality of pre-defined points to couple the plurality ofpre-defined points with the plurality of slave inverter circuits and anauxiliary power supply. The auxiliary power supply provides power tooperate the plurality of slave inverter circuits, the master controllermodule, the un-folder circuit, a communication controller and otherassociated circuits. The auxiliary power supply adapted to be triggeredat a plurality of voltage levels associated with a design of the groupof cells. The wave shaper circuit comprising a Phase shift full bridgezero voltage switch (ZVS) circuit and a diode loss recovery circuit.

In an example, the present invention also includes related methods tocarryout the functionality of the circuits and systems described herein.In an example, the present invention provides a method for operating aninverter device. The method includes generating a rectified DC waveformusing a slave inverter circuit, filtering an AC current ripple back tothe DC source, boosting the rectified DC waveform to an intermediary12-15 voltage range, shaping the rectified DC waveform to a half waverectified 120V to 240V waveform, recovering energy using the rectifierenergy recovery circuit during a switching operation, generating a PWMwaveform using either an analog mixed signal module or digitalcontroller module, synchronizing the rectified DC waveform to a gridvoltage, and managing a plurality of sense circuits coupled to theplurality of solar cells to record a cell group voltage and a cell groupcurrent. In an example, the present method further includes generating areference signal for each of the analog mixed signal control modules toturn off/on the rectified DC waveform from each of the inverter devicesto a power-line grid.

In an example, the storage device comprises a capacitor configuredbetween a first terminal and a second terminal of the rectifier output.In an example, the second terminal is at a ground terminal. In anexample, the energy recovery circuit further comprises a node betweenthe capacitor and the second terminal. The node is at an output voltageof the output of the DC bus structure. In an example, the energyrecovery circuit includes a first p-n diode configured between the nodeand the second terminal. The first p-n diode is configured to maintainthe node at the output voltage. In an example, the rectifier circuitdevice comprises a full bridge diode circuit coupled with the energyrecovery circuit. In an example, the energy recovery circuit furthercomprising an inductor coupled to the first terminal. The inductor is inparallel to the storage capacitor and in series with the first p-njunction diode. In an example, the energy recovery circuit furthercomprising a second p-n junction diode provided between the first p-njunction diode and the storage capacitor. The second p-n junction diodeis coupled to an output terminal of the DC bus structure. In an example,the second p-n junction diode is configured to allow a switching currentto flow to the output terminal. In an example, the energy recoverycircuit is configured with the inverter device, which is coupled to agroup of solar cells. In an example, the group of solar cells isprovided in a solar module. In an example, the storage capacitor ismetal or ceramic filled capacitor structure having a capacitancedetermined by a frequency of switching on the rectifier circuit, thereverse recovery charge, and a voltage across the rectifier output.

In an alternative specific embodiment, the present invention provides amethod of operating an inverter device configured on a back plane of asolar module, the inverter device comprising an energy recovery circuitdevice coupled to a rectifier circuit, the method comprisingtransferring a charge from a rectifier output to a storage capacitorconfigured in an energy recovery circuit; storing the charge at thestorage capacitor for a time period associated with a reverse recoverytime; and transferring the charge to an output of a DC bus structure toreduce a diode recovery loss in the rectifier circuit. Further detailsof the present method can be found throughout the present specificationand more particularly below.

It should be understood that the description recited above is an exampleof the disclosure and that modifications and changes to the examples maybe undertaken which are within the scope of the claimed disclosure.Therefore, the scope of the appended claims should be accorded thebroadest interpretation so as to encompass all such modifications andsimilar arrangements, including a full scope of equivalents.

What is claimed is:
 1. An inverter device configured on a back plane ofa solar module, the inverter device comprising an energy recoverycircuit coupled to a rectifier circuit at a first node and a secondnode, the energy recovery circuit comprising: a first diode; a seconddiode; an inductor; and a storage device coupled to a rectifier outputfrom a rectifier circuit, the energy recovery circuit being configuredto temporarily store a reverse recovery charge and transfer the reverserecovery charge to an output of a DC bus structure comprising the secondnode and a third node to reduce a diode recovery loss in the rectifiercircuit; wherein the inductor has a first end connected to the firstnode and a second end connected to the third node, the first diode isconnected to the storage device at a fourth node, the first diode andthe storage device are connected between the first node and the secondnode, and the second diode has a first end directly connected to thesecond end of the inductor and a second end directly connected to thefourth node.
 2. The device of claim 1 wherein the storage devicecomprises a capacitor, and wherein the second node is a ground node. 3.The device of claim 1, wherein the first diode is configured to maintainthe third node at the output voltage.
 4. The device of claim 3 whereinthe rectifier circuit comprises a full bridge diode circuit coupled withthe energy recovery circuit.
 5. The device of claim 1, wherein thesecond diode is configured to enable a switching current to flow to theoutput terminal.
 6. The device of claim 1, wherein the inverter deviceis coupled to a group of solar cells.
 7. The device of claim 6 whereinthe group of solar cells is provided in the solar module.
 8. The deviceof claim 1 wherein the storage device is a metal or ceramic filledcapacitor structure having a capacitance determined by a frequency ofswitching on the rectifier circuit, the reverse recovery charge, and avoltage across the rectifier output.
 9. A method of operating aninverter device configured on a back plane of a solar module, theinverter device comprising an energy recovery circuit coupled to arectifier circuit at a first node and a second node, the energy recoverycircuit comprising a first diode, a second diode, an inductor, and astorage device, wherein the inductor has a first end connected to thefirst node and a second end connected to a third node, the first diodeis connected to the storage device at a fourth node, the first diode andthe storage device are connected between the first node and the secondnode, and the second diode has a first end directly connected to thesecond end of the inductor and a second end directly connected to thefourth node, the method comprising: transferring a charge from arectifier output to the storage capacitor storing the charge at thestorage capacitor for a time period associated with a reverse recoverytime; and transferring the charge to an output of a DC bus structure toreduce a diode recovery loss in the rectifier circuit, the outputcomprising the second node and the third node.
 10. The method of claim9, wherein the storage device comprises a capacitor, wherein the secondterminal is a ground node.
 11. The method of claim 9, wherein the firstdiode is configured to maintain the third node at an output voltage. 12.The method of claim 11 wherein the rectifier circuit comprises a fullbridge diode circuit coupled with the energy recovery circuit.
 13. Themethod of claim 12, wherein the second diode is configured to enable aswitching current to flow to the output terminal.
 14. The method ofclaim 9, wherein the energy recovery circuit is configured with theinverter device, the inverter device being coupled to a group of solarcells; wherein the group of solar cells is provided in a solar module;wherein the storage device is a metal or ceramic filled capacitorstructure having a capacitance determined by a frequency of switching onthe rectifier circuit, the reverse recovery charge, and a voltage acrossthe rectifier output.